Histidine is an amino acid and belongs to the class which has acid or base R-groups. Initially thought essential only for infants, it has now been shown in longer-term studies to be essential for adults also.

Histidine was first isolated by German physician Albrecht Kossel and Sven Gustaf Hedin in 1896. It is also a precursor to histamine, a vital inflammatory agent in immune responses.

The acid-base properties of the imidazole side chain are relevant to the catalytic mechanism of many enzymes. In a histidine proton shuttle, histidine is used to quickly shuttle protons. It can do this by abstracting a proton with its basic nitrogen to make a positively charged intermediate and then use another molecule, a buffer, to extract the proton from its acidic nitrogen.

Histidine forms complexes with many metal ions, for example the axial base attached to Fe in myoglobin and hemoglobin.

* Amino acids which are essential amino acids which cannot be made by the human body and, therefore, must be obtained in the diet.

  • Three histidines are used as a framework for binding the metal zinc in the important enzyme carbonic anhydrase which helps carry CO2 to the lungs.
Histidine wiki

Biochemical concepts

Chemistry concepts

Tillery, Enger and Ross
Ch 14

HyperPhysics*****Chemistry *****Organic Chemistry R Nave
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